Impact of the Autumn Kara Sea Ice on Opposite Temperature Anomalies in December of 2020 and 2021 in Beijing-Tianjin-Hebei Region
The temperature is abnormally low in December 2020 in Beijing-Tianjin-Hebei region,while has the opposite trend in December 2021.Although La Nina occurring during both winter,there are obvious differences in the Kara Sea sea ice anomaly in autumn,which may be the potential external forcing signal of the opposite temperature trends.The sea ice in the Kara Sea caused the atmospheric circulation anomaly through the difference of the meridional gradient of temperature in the middle and high latitudes,which led to the temperature anomaly in December in Beijing,Tianjin and Hebei.Sea ice was anomalous less in the key areas of the Kara Sea in autumn of 2020,leading to intensified Siberian high and the blocking high in the Ural Mountains and a typical dimensional pattern prevailing over Eurasian continent in December 2020,which favored low temperatures in Beijing-Tianjin-Hebei region.Sea ice in autumn of 2021 and atmospheric circulation in December 2021 were opposite to the trend of 2020.